1. Field of the Invention
The present invention relates generally to solid-state optical elements, and more particularly, to a quasi-monolithic saturable optical element that provides for saturable absorption, polarization, and retroreflection in a single solid-state optical element.
2. Description of Related Art
Each of the individual functions performed by the present invention (saturable absorption, polarization, and retroreflection) is generally well known in the art. Saturable absorbers are well-known in the art. Brewster's angle orientation for polarization selection is well known. Dielectric high reflection coatings can be deposited on substrates without difficulty using conventional practices. Although individual devices exist that perform each of the above functions, the disadvantages and difficulties associated with aligning three functionally different elements are believed to be self-evident.
By way of example, U.S. Pat. No. 4,084,883, entitled "Reflective Polarization Retarder and Laser Apparatus Utilizing Same", issued to Eastman et al. discloses a reflective polarization layer for a laser element. U.S. Pat. No. 4,104,598 entitled "Laser Internal Coupling Modulation Arrangement with Wire Grid Polarizer Serving as a Reflector and Coupler", issued to Abrams discloses a laser having a combined reflector and wire grid polarizer. U.S. Pat. No. 4,875,220 entitled "Laser Tube for Polarized Laser Emission", issued to Krueger et al., has two integrated laser mirrors, and the integrated mirror has a polarizing surface thereon. U.S. Pat. No. 5,097,481 entitled "Gas Laser Having Two Longitudinal Modes of Laser Oscillation", issued to Fritzsche et al. is similar to the Krueger et al. patent. U.S. Pat. No. 5,101,415 entitled "Laser Resonator Mirror with Wavelength Selective Coatings on Two Surfaces", issued to Kolb et al. discloses a laser mirror having reflective surfaces which operate in first and second wavelength modes.
In addition to the above-cited patents, prior work relating to solid-state saturable absorbers is typified by the following publications. An article entitled "Formation, optical properties, and laser operation of F.sub.2 - centers in LiF", by W. Gellermann et al., in J. Appl. Phys., 61, 1297 (1987) investigates the formation conditions, optical properties, and lasing behavior of F.sub.2 - color centers in LiF crystals. An article entitled "Phototropic centers in chromium-doped garnets", by L. I. Krutova et al., in Opt. Spectrosc (USSR), 63, 695 (1987) discusses the use of chromium-doped garnets as passive Q switches. A presentation entitled "Room temperature Q-switching of Nd:YAG by F.sub.2 - color centers in LiF," presented by D. S. Sumida et al., CLEO, San Francisco, Calif., Paper WM5 (1986), discusses research on the passive Q-switch properties of F.sub.2 -:LiF, a color center material of interest for solid-state laser designs because of its saturation behavior at high intensity levels. An article entitled "Room Temperature Laser Action and Q-Switching of F- Aggregate Color Centers in LiF" by S. C. Rand, et al., presented at the 5th International Conference on Dynamical Processes in the Excited State of Solids, Lyon, France, Jul. 1-4, 1985, indicates that passive Q-switching by F.sub.2 - centers in gamma-irradiated LiF produced 30 ns Nd:YAG pulses. An article entitled "Photochromic properties of a gadolinium-scandium-gallium garnet crystal," by E. V. Zharikov et al, Preprint #238, USSR Academy of Sciences, Institute of General Physics, Moscow (1985) discusses the photochromic properties of a GSGG:Cr, Nd crystals.
However, the above-cited prior art does not disclose combining three functions (saturable absorption, polarization, and retroreflection) into one element and no such prior art devices appear to exist. Therefore, it is an objective of the present invention to provide a quasi-monolithic saturable optical element that provides for saturable absorption, polarization, and retroreflection in a single solid-state optical element.